The mobility of W atoms on the (320) and (221) regions of a W microcrystal surface with a tip curvature radius of about 300nm was investigated via spectral analysis of field emission current fluctuations at 500 to 800K. The diffusion appeared to be one-dimensional for W(320) and two-dimensional for W(221). The surface-diffusion coefficients were determined by comparison of the experimental results with theoretical spectral density functions. The results could be described by:

(320):     D (cm2/s) = 4.4 x 10-7 exp[-0.48(eV)/kT]

(221):     D (cm2/s) = 3.7 x 10-2 exp[-1.07(eV)/kT]

T.Biernat, R.Błaszczyszyn: Applied Surface Science, 2009, 255[13-14], 6593-7